unit Bee_Crc;

{ Contains:

  Routines for Crc32 calculating (c) 1998 Dmitry Auzhin;
  Table is calculated by Sasha Leshinsky.

  (C) 1998 Dmitry Auzhin;
  (C) 1999-2005 Andrew Filinsky.

  Modifyed:

  v0.7.8 build 0153 - 2005/07/08 by Andrew Filinsky.
}

{$I Compiler.inc}

interface

uses
  Classes,     // TFileStream class, ...
  SysUtils;    // fmXXX constants.

// Crc32 calculating routines ...

  procedure UpdCrc32    (var   aCrc32: cardinal; aData: byte);
  function  UpdateCrc32 (const aCrc32: cardinal; aData: byte): cardinal;
  function  Crc32File   (const aFileName: string): cardinal;
  function  Crc32Str    (const aString: string): cardinal;

implementation

const
  Crc32Tab: array [0..255] of cardinal = (
    $00000000,$77073096,$EE0E612C,$990951BA,$076DC419,$706AF48F,$E963A535,$9E6495A3,
    $0EDB8832,$79DCB8A4,$E0D5E91E,$97D2D988,$09B64C2B,$7EB17CBD,$E7B82D07,$90BF1D91,
    $1DB71064,$6AB020F2,$F3B97148,$84BE41DE,$1ADAD47D,$6DDDE4EB,$F4D4B551,$83D385C7,
    $136C9856,$646BA8C0,$FD62F97A,$8A65C9EC,$14015C4F,$63066CD9,$FA0F3D63,$8D080DF5,
    $3B6E20C8,$4C69105E,$D56041E4,$A2677172,$3C03E4D1,$4B04D447,$D20D85FD,$A50AB56B,
    $35B5A8FA,$42B2986C,$DBBBC9D6,$ACBCF940,$32D86CE3,$45DF5C75,$DCD60DCF,$ABD13D59,
    $26D930AC,$51DE003A,$C8D75180,$BFD06116,$21B4F4B5,$56B3C423,$CFBA9599,$B8BDA50F,
    $2802B89E,$5F058808,$C60CD9B2,$B10BE924,$2F6F7C87,$58684C11,$C1611DAB,$B6662D3D,
    $76DC4190,$01DB7106,$98D220BC,$EFD5102A,$71B18589,$06B6B51F,$9FBFE4A5,$E8B8D433,
    $7807C9A2,$0F00F934,$9609A88E,$E10E9818,$7F6A0DBB,$086D3D2D,$91646C97,$E6635C01,
    $6B6B51F4,$1C6C6162,$856530D8,$F262004E,$6C0695ED,$1B01A57B,$8208F4C1,$F50FC457,
    $65B0D9C6,$12B7E950,$8BBEB8EA,$FCB9887C,$62DD1DDF,$15DA2D49,$8CD37CF3,$FBD44C65,
    $4DB26158,$3AB551CE,$A3BC0074,$D4BB30E2,$4ADFA541,$3DD895D7,$A4D1C46D,$D3D6F4FB,
    $4369E96A,$346ED9FC,$AD678846,$DA60B8D0,$44042D73,$33031DE5,$AA0A4C5F,$DD0D7CC9,
    $5005713C,$270241AA,$BE0B1010,$C90C2086,$5768B525,$206F85B3,$B966D409,$CE61E49F,
    $5EDEF90E,$29D9C998,$B0D09822,$C7D7A8B4,$59B33D17,$2EB40D81,$B7BD5C3B,$C0BA6CAD,
    $EDB88320,$9ABFB3B6,$03B6E20C,$74B1D29A,$EAD54739,$9DD277AF,$04DB2615,$73DC1683,
    $E3630B12,$94643B84,$0D6D6A3E,$7A6A5AA8,$E40ECF0B,$9309FF9D,$0A00AE27,$7D079EB1,
    $F00F9344,$8708A3D2,$1E01F268,$6906C2FE,$F762575D,$806567CB,$196C3671,$6E6B06E7,
    $FED41B76,$89D32BE0,$10DA7A5A,$67DD4ACC,$F9B9DF6F,$8EBEEFF9,$17B7BE43,$60B08ED5,
    $D6D6A3E8,$A1D1937E,$38D8C2C4,$4FDFF252,$D1BB67F1,$A6BC5767,$3FB506DD,$48B2364B,
    $D80D2BDA,$AF0A1B4C,$36034AF6,$41047A60,$DF60EFC3,$A867DF55,$316E8EEF,$4669BE79,
    $CB61B38C,$BC66831A,$256FD2A0,$5268E236,$CC0C7795,$BB0B4703,$220216B9,$5505262F,
    $C5BA3BBE,$B2BD0B28,$2BB45A92,$5CB36A04,$C2D7FFA7,$B5D0CF31,$2CD99E8B,$5BDEAE1D,
    $9B64C2B0,$EC63F226,$756AA39C,$026D930A,$9C0906A9,$EB0E363F,$72076785,$05005713,
    $95BF4A82,$E2B87A14,$7BB12BAE,$0CB61B38,$92D28E9B,$E5D5BE0D,$7CDCEFB7,$0BDBDF21,
    $86D3D2D4,$F1D4E242,$68DDB3F8,$1FDA836E,$81BE16CD,$F6B9265B,$6FB077E1,$18B74777,
    $88085AE6,$FF0F6A70,$66063BCA,$11010B5C,$8F659EFF,$F862AE69,$616BFFD3,$166CCF45,
    $A00AE278,$D70DD2EE,$4E048354,$3903B3C2,$A7672661,$D06016F7,$4969474D,$3E6E77DB,
    $AED16A4A,$D9D65ADC,$40DF0B66,$37D83BF0,$A9BCAE53,$DEBB9EC5,$47B2CF7F,$30B5FFE9,
    $BDBDF21C,$CABAC28A,$53B39330,$24B4A3A6,$BAD03605,$CDD70693,$54DE5729,$23D967BF,
    $B3667A2E,$C4614AB8,$5D681B02,$2A6F2B94,$B40BBE37,$C30C8EA1,$5A05DF1B,$2D02EF8D);

// Crc32 calculating routines ...

  procedure UpdCrc32 (var aCrc32: cardinal; aData: byte);
  var
    Temp: cardinal;
  begin
    Temp   := aCrc32;
    aCrc32 := Crc32Tab [byte (Temp xor aData)] xor (Temp shr 8);
  end;

  function UpdateCrc32 (const aCrc32: cardinal; aData: byte): cardinal;
  begin
    Result := Crc32Tab [byte (aCrc32 xor aData)] xor (aCrc32 shr 8);
  end;

  function Crc32File (const aFileName: string): cardinal;
  const
    BufferSize = 65536;
  var
    Stream: TFileStream;
    Buffer: array [0..BufferSize - 1] of byte;
    Readed: integer;
    I: integer;
  begin
    Result := cardinal (-1);

    try
      Stream := TFileStream.Create (aFileName, fmOpenRead or fmShareDenyWrite);
    except
      Stream := nil;
    end;

    if Stream <> nil then
    begin
      repeat
        Readed := Stream.Read (Buffer, SizeOf (Buffer));
        for I := 0 to Readed - 1 do
          Result := UpdateCrc32 (Result, Buffer [I]);
      until Readed = 0;
      Stream.Free;
    end;

    Result := not Result;
  end;

  function Crc32Str (const aString: string): cardinal;
  var
    I: Integer;
  begin
    Result := cardinal (-1);
    for I := 1 to Length (aString) do
      Result := UpdateCrc32 (Result, Ord (aString [I]));
    Result := not Result;
  end;

end.
